Hydrodesulfurization of a coked hydrocarbon stream comprising gasoline constituents and gas oil constituents



Aug. 25, 1959 D. E. COOK ETAL HYDRODESULFURIZATION OF A COKED HYDROCARBON STREAM COMPRISING GASOLINE CONSTITUENTS AND GAS OIL CONSTITUENTS Filed May 17, 1954 EDWARD J. BARRASSO ATTORNEY INITIAL REACTOR United States Patent dice 2,901,417 Patented Aug. 25, 1959 HYDRODESULFURIZATION F A COKED HYDRO- CARBN STREAMI CMPRISHNG GASOLINE CONSTITUENTS AND GAS OIL CONSTITUENTS David E. Cook, East Orange, and Edward J. Barrasso,

Newark, NJ., assignors to Esso Research and Engineering Company, a `corporation of Delaware Application May 17, 1954, Serial No. 430,234 5 Claims. (Cl. 208-97) The invention is broadly concerned with the hydrodesulfurizaton of hydrocarbon streams comprising hydrocarbons boiling in the motor fuel and in the gas oil boiling ranges. The invention is more particularly concerned with the treatment of particular streams derived from heavy residual coking operations. In accordance with the present invention high quality petroleum products are secured by employing a two-stage hydrodesulfurization operation. In the initial stage a heavy gas oil fraction, preferably blended with a `desulfurized gas oil produced in the process, is desulfurized. In the second stage the product from the initial reaction is blended with a stream comprising heavy naphtha constituents and relatively low boiling heating oil constituents. The reaction product from the secondary stage is handled in order to segregate a heavy gas oil fraction, a part of which is preferably recycled with the fresh feed to the initial stage. A preferred adaptation of the present invention is for the treatment of streams derived from heavy residual coking operations.

In order to secure a satisfactory hydrodesulfurization operation, normally the operating conditions employed for the hydrodesulfurization of constituents boiling in the motor fuel boiling range are appreciably `different from the operating conditions employed for the hydrodesulfurization of constituents boiling above the motor fuel boiling range as, for example, constituents boiling in the heating oil boiling range and in the gas oil boiling range. Typical temperatures employed 4for the hydrodesulfurization of a heavy naphtha fraction boiling in the motor fuel boiling range are in the range from about 600 F. to 700 F. Pressures are in the range from about 5 0` lbs. per square inch to 400 lbs. per square inch. The feed rates are generally in the range from about 1 to 8 volumes of naphtha per volume of catalyst per hour. This heavy naphtha fraction boils in the range from about 250 F. to 430 F.

On the other hand, when hydrodesulfurizing a gas oil boiling in the range from about 430 F. to 1050 F., the temperatures are usually in the range from about 675 F. to 800 F., preferably in the range from about 700 F. to 750 F. Pressures are about 200 lbs. per/square inch to 1000 lbs. per square inch, preferably in the range from 200 lbs. per `square inch to 400 lbs. per square inch. The feed rates are about 0.5 to 4.0 volumes of oil per volume of catalyst per hour.

The catalyst for hydrodesulfurization operation may be any satisfactory hydrofining catalyst, as for example a mixture of cobalt oxide and molybdenum oxide. A preferred catalyst comprises 12% cobalt molybdate on alumina. Other satisfactory catalysts are sulfides of nickel and tungsten which may be on a carrier such as alumina.

Also with respect to naphtha and gas oil fractions derived from the coking of heavy residual fractions, as for example those residuals having gravities below about 15 A.P.I., a particular problem arises. While the processing of the coker fractions boiling above about 400 F. in a hydrodesulfurization can be satisfactorily controlled,

the coker naphtha on the other hand due to the presence of a relatively large quantity of mono-olelins and diolefins is extremely exothermic in the hydrodesulfurization operation. Tlie heat liberated gives a marked temperature rise during the reaction with adverse results. While this temperature rise can be controlled it is difficult and expensive.

The heavy residual coking operation may be carried out by a number of processes as, for example, by a fluid coking or fixed bed operation. The fluid coldng process employs no catalyst and depends upon a circulating stream of nely divided coke particles to furnish heat and a large amount of surface to accomplish the coking reaction. The operation requires the use of a burner vessel and a reaction vessel with the necessary standpipes and transfer lines to accomplish the circulation of fluidized coke between the two vessels. The fluidized coke is continually formed in the process and it is partly burned to supply heat. The bulk of the coke is withdrawn from the system as a by-product.

The `feed to the coking operation is usually a bottoms stream from a vacuum distillation operation and may comprise from about 4% to 50% of the crude depending upon the source and character of the crude. The temperatures employed in the coking operation may vary appreciably but are generally in the range from about 850 F. to 1050 F. in the coking zone. The pressures in the coking zone are generally in the range from about 5 lbs. per square inch to 50 lbs. per square inch. The temperatures in the burning zone are in the range from about 1100 F. to 1200 F. while the pressures are in the range from about 15 lbs. per square inch to 50 lbs. per square inch.

The products secured from a fiuid coking operation processing residual stock are high in sulfur and are relatively unstable. However, hydrogenation provides a satisfactory means of converting the raw unstable Coker products into finished low sulfur products with good stability. As mentioned, hydrodesulfurization of coker gas oil (boiling in the range from about 430 F. to 1050 F.) can be accomplished without difficulty. However, hydrodesulfurization of Coker naphtha due to the presence of unsaturated constituents is extremely exothermic. The heat liberated tends to give a marked temperature rise during the reaction.

In accordance with the present invention a blend of coker naphtha and coker gas oil are hydrodesulfurized in a mixed vapor-liquid phase operation. When operating in this manner the temperature rise in the reactor is minimized by the high heat capacity of the liquid phase gas oil and by the tendency of this gas oil to vaporize further as the temperature tends to rise. An operation of this character tends to adversely affect the octane number of the motor fuel. However, the process is entirely satis-factory when loss of octane number of the naphtha is not important, as for example when the naphtha is used as vfeed to a hydroforming operation or as diesel fuel. However, hydrodesulfurization of the blend does have the typical disadvantage of treating a wide boiling range feed stock. The conditions required lfor the hydrodesulfurization of the gas oil are overly severe for the hydrodesulfurization of the naphtha to be blended in motor gasoline. In accordance with the present invention these disadvantages are overcome.

The invention may be more fully understood by reference to the drawing illustrating one adaptation of the same. In the drawing the invention is described with respect to the handling of a hydrocarbon fraction secured from a coking operation. Referring specifically to the drawing, a heavy residual oil as, for example, one boiling above about 950 F. and having a gravity in the range .from about` A.P.I. to 20 A.P.I. is introduced intocoker reaction zone 1 by means of feed line 2. Steam is introduced into zone 1 by means of line 3 which maintains the particles of coke in the lluidized state. vC olfe particles are withdrawn from the bottom of zone 1 by means of line V4- and passed to a burner ,zone (not yshown).`A In the burner zone portions of the coke particles are burned and VYa portion of these hot coke particles are returned by means of line 50 to colrer zone 1. Reaction zone 1 is operated at a temperature in the range vfrom about 840 F. -to 1120 F. and a pressure in the range from about 14 to 55 lbs. per square inch guage.

Vapo-rized products are removed overhead from coker zone "1'by means of line 5 at a ytemperature in the range `from about 850 to 1100 F. These products `are passed through a cooling zone 6. The cooled products adeintroduce'd into a separation or distillation zone 11 by rneans of line 9. "Temperature and pressure conditions in zone 11 -are adapted to remove overhead by means of line 12 light hydrocarbon constituents boiling below about 250 to 275 Thisstream is passed to a separation or distillation zone 13 `maintained under conditions to remove overhead by means of line 14 hydrocarbons boiling below the motor lfuel boiling range (about 80 F. to 100 F.). Light hydrocarbon constituents boiling in the range from about 100 F. to 275 F. are removed by means of line 15 and preferably blended with hydrodesulfurized heavy naphtha constituents. Water is removed from zone 13 by means of' line 16.

l' Separation zone 11 is operated under temperature and pressure conditionsV adapted to segregate a stream comprising heavy naphtha constituents and heating oil constituents (boiling range about 250 F. to 730 F.) This stream isiremoved from separation zone 11 by means of Iine`"17.' A heavy gas oilfraction boiling in the range from" about 700 F.u to 1050 F. is removed from distillation zone 11 by means of line 18. Hydrocarbon constituents boiling above about 1075 F. are separated asa liquid phase by means of line 46 and are preferably recycled to coking zone 1.

The heavy gas oil stream is mixed with hydrogen intro'duced by means of line 19 or with recycled hydrogen introduced by means ofV line and passed to an initial lmiydrodesulfurization zone 21. Hydrodesulfurization zone 2 1 `:is operated at a temperature in the range from about 500ov F. to 800 F. and at a pressure inthe range from about 100 to 1000 lbs. per square inch guage. The feed rate is in the range of about 0.5 to 4.0 volumes of oil per volume of catalyst per hour. The catalyst comprises cobalt molybdate supported on alumina.

" A particular adaptation of the present invention is to blend with the heavy gas oil feed a portion of desulfurized gas oil prior `to passing the heavy gas oil feed to the initial hydrodesulfurization zone. The amount o-f deslfuriz=d gas oil blended is in the range from about 0.5 venirne" to 4.0 volumes based 'upon the heavy gas oil. The'tempera'ture of the desulfurized gas oil will be in the range of about 650 F. to 800 F. and willbe at a higher heat level than the heavy gas oil. Thus, it can be used to preheat to inlet temperature the heavy gas oil feed to hydrodesulfurization Zone 21 by admixing.

The desulfurized gas oil stream is withdrawn from initial hydrodesulfurization zone 21 by means of line 22 and inJ accordance with the present invention is blended with heating oilfnaphtha lfraction segregated in distillation zone 11 and passed to a secondary hydrodesulfurization zone 23. The volume of heavy gas oil used is at least equal to the volume of heavy naphtha-light gas oil and is preferably from 2 to 3 times the volume of the heavy naphthalight gas oil.

Additional hydrogen may be mixed with the feed stream by means of line 24 or recycled hydrogen may be added by means of line 25,. Zone 23 may be operated at a somewhat higher temperature chosen from the range of from about 650 to 800 F.

The hydrodesulfurized hydrocarbon fraction boiling in the range of about 250 F. to l050 F. is removed from secondary desulfurization zone 23 by means of line 26. This fraction is cooled in partial condenser 27 and passed to a separation zone 28 wherein desulfurized heavy gas oil constituents are condensed. This liquid phase removed by means of line 29 and at least a portion recycled by means of line 30 with the heavy gas oil feed `to zone In accordance with the present invention a portion of this condensate may be passed to a distillation Vzone 31 by means of a line 32. The condensate boils in the range from abou-t650 F. to 1025" FQ l Y i '4 Uncondensed constituents are removed as a vapor stream from zone 28 by means of line 33 and passed to separation zone 34. Zone 34 is operated under conditions to condense `the hydrodesulfurization product which is removed as a liquid stream by means of line 35. Recycle hydrogen is removed from zone 34- by means of line 36 and is preferably recycled to zone 21 and zone 23. The hydrodesulfurized product is passed to distillation zone 31 wherein the temperature and pressure condif tions are adapted to segregate the desired hydrocarbon fractions. A heavy naphtha fraction may be removed from zone 31 by means of line 37, a heating oil fraction by means of line 38, gas oil fraction by lines 39 and d() and residuum fraction by lines 41. These hyd-rodesulfurized streams may then be blended as desired with other streams.

What is claimed is:

l. A combination process for upgrading heavy residualV petroleum oil which comprises in combination, coldng said residual oil at a temperature in the range of about 350 to 1050 F., distilling the Coker products to segregate a heavy naphtha-heating oil fraction boiling in the range of `from about 250 to about 730 F. and a heavy gas oil fraction boiling in the range of from about 700 to 1050 F., adding hydrogen and desulfurized gas oil to said heavy gas oil fraction and passing the resultant mixture through an initial hydrodesulfurization zone to effect a substantial reduction in the sulfur content of said heavy gas oil fraction combining the effluent from said initial hydrodesulfulization zone with said heavy naphtha-heating oil `fraction and passing the same into a secondary hydrodesulfurization Zone to effect a substantial reduction in the sulfur content of said heavy naphtha-heating oil fraction, partially condensing effluent from said secondary hydrodesulfurization zone to segregate desulfurized gas oil for addition to the heavy gas oil feed to the initial hydrodesulfurization Zone, condensing the normally liquid hydrocarbons, separating hy-y drogen-containing gas from the condensate and fractionating the condensate to segregate motor fuel and heating oil fractions of low sulfur content.

2. The process as defined in claim 1 in which the desulfurized gas oil separated from the etlluent from the secondary hydrodesulfurization zone is at a temperature of about 650 to 800 F. when combined with the heavy gas oil feed to the initial hydrodesulfurization zone.

3. The process as dened in claim 2 in which the amount of desulfurized gas oil recycled is from about 0.5 to 4 volumes per volume of heavy gas oil feed.

4. The process as dened in claim 3 in which the amount of efuent from said initial hydrodesulfurization Zone which is combined with heavy naphtha-lieating oil fraction for feeding to said secondary hydrodesulfuriza tion zone is in the ratio of about 2 to 3 volumes of the former per volume of the latter.

5. The process as defined in claim l in which the initial hydrodesulfurization zone is operated ata term perature of from about 500 to 800 F., a pressure'of from` to 1000 p.s.i.gi. and a space velocity of 0.5 to 40 volumes Qf Oil Per volume t Catalyst per haar and said secondary hydrodesulfurization zone is operated at a higher temperature in the range of from 650 to References Cited in the le of this patent 6 Hudson Mar. 13, 1945 Cole Dec. 2, 1947 Franklin Mar. 4, 1952 Porter et al. Mar. 16, 1952 Hartley Oct. 12, 1954 

1. A COMBINATION PROCESS FOR UPGRADING HEAVY RESIDUAL PETROLEUM OIL WHICH COMPRISES IN COMBINATION, COKING SAID RESIDUAL OIL AT A TEMPERATURE IN THE RANGE OF ABOUT 850 TO 1050*F., DISTILLING THE COKER PRODUCTS TO SEGREGATE A HEAVY NAPHTHA-HEATING OIL FRACTION BOILING IN THE RANGE OF FROM ABOUT 250 TO ABOUT 730*F. AND A HEAVY GAS OIL FRACTION BOILING IN THE RANGE OF FROM ABOUT 700 TO 1050*F. ADDING HYDROGEN AND DESULFURIZED GAS OIL TO SAID HEAVY GAS OIL FRACTION AND PASSING THE RESULTANT MIXTURE THROUGH AN INITIAL HYDRODESULFURIZATION ZONE TO EFFECT A SUBSTANTIAL REDUCTION IN THE SULFUR CONTENT OF SAID HEAVY GAS OIL FRACTION COMBINING THE EFFLUENT FROM SAID INITIAL HYDRODESULFURIZATION ZONE WITH SAID HEAVY NAPHTHA-HEATING OIL FRACTION AND PASSING THE SAME INTO A SECONDARY HYDRODESULFURIZATION ZONE TO EFFECT A SUBSTANTIAL REDUCTION IN THE SULFUR CONTENT OF SAID HEAVY NAPHTHA-HEATING OIL FRACTION, PARTIALLY CONDENSING EFFLUENT FROM SAID SECONDARY HYDRODESULFURIZATION ZONE TO SEGREGATE DESULFURIZED GAS OIL FOR ADDITION TO THE HEAVY GAS OIL FEED TO THE INITIAL HYDRODESULFURIZATION ZONE, CONDENSING THE NORMALLY LIQUID HYDROCARBONS SEPERATING HYDROGEN-CONTAINING GAS FROM THE CONDENSATE AND FRACTIONATING THE CONDENSATE TO SEGREGATE MOTOR FUEL AND HEATING OIL FRACTION OF LOW SULFUR CONTENT. 